I just wanted to leave some feedback on two Tetroid products I bought.

The first is the ROM switcher. This is a very simple design, very well executed. There are SMD components on both sides of the board. The main components are a 29F040 flash and a 74HCT00 for /CE & /OE inversion. It has an optional adapter board for reprogramming it, and I strongly recommend you buy this board when you buy your ROM switcher - I didn't and I already regret it. The quality of assembly is high. Five stars.

The second is the backplane. This is a 2-part black PCB. The first PCB is the buffer board, which contains a small 78M05 D-PAK voltage regulator and three 74HCT245s. This means only 12 lines are being buffered, by level shifting to 5V and using the characteristics of the IC to clean up the edges of the signal on transitions. I did not check which signals are being buffered, but the usual suspects would be most of the control signals, /ROMOE, etc. The PCBs are black, which is a nice touch as they're visible outside the QL. One small cosmetic blunder is that on the backplane board, the silk layer word "<-QL" is printed inverted, so when it's inside your QL it is upside down. However, this is the most trivial of distractions. If it bothers me too much, I can use a black paint pen (not a sharpie!) to hide it. There is a 20 pin DIP socket that is unpopulated and I do wonder what goes there and what it does.

Overall, the packaging was excellent. It came from Russia with tracking in a right-sized box, in anti-static plastic sealed to the perfect size. The overall presentation when opening the box was excellent.

A simple half sheet of paper explaining the functions and features of each product would have been useful for some customers. Their absence was no problem to anyone who's owned a QL for years, but for new or returning QLers knowing where to put a replacement ROM cannot be taken for granted.